I also, have been getting special offers for games I own.

See, I don't get this claim. Why would anyone go to the effort to make it "less likely" you will get offered a game you already own, but not simply make it so that you *won't* get offered a duplicate game? Seriously, why? If you can reduce the chance of getting a duplicate, you should be able to reduce the probability of that event to zero. If anything, it should be easier to eliminate offers of games people own through GOG than to make it "less likely".

Many established GOG customers already own hundreds of GOG games. I've personally got a few hundred games -- but I also have probably another hundred games on my wish list. Some of my wish list games *are* on the list of reported offers. It would be nice if I were offered some of the games I wish to purchase -- especially since they are willing to offer deals on those games to other people.

[P.S. Amazon used to offer personalized "gold box" deals, and those offerings were largely drawn from items that were on a wish list or in the "save for later" portion of your shopping cart. Alternatively, they were drawn from "customers who bought X frequently bought Y" calculations. Most relevantly, they never included items you had already purchased from Amazon. This isn't a radical concept.]

FWIW, so far my two mystery box offers have been for games that I don't own.

I've got about 75 games in my account - my guess is that that's many more than most GOG customers (most of whom I'll bet never visit the forum, much less post on it), but less than most forum posters with significant rep.

Probably because nobody can rule out bugs.

You are on GOG here. Poor software design is like their second name when it comes to web programming :-P